I like the idea of 3D printers. You have a device that can repeatable produce low volume, highly customizable items. This won't change the Henry Ford assembly line approach. The assembly line is great at producing large quantities of exact copies.
So, it stands to reason the best initial application for 3D printing would be clothing. Clothing has very high variety (style, color, shape, size, etc), and thus low volume. (With the assumption that the current size system is a generalization to help mass production.)
Use Case:
You walk into a store full of samples, and find something you like. Step into the 3D scanner for measurements (already exists, and in limited use). The printer then prints a tailored shirt, shorts, etc.
The new "Old Navy" would maintain its standing by using different materials, machines, designs, and public image. Thus duplicating the current model.
The scanner would not be required for clothing production, you could save your last scan and provide it to the store.
It could also be applied to online shopping. You order a pattern and take it to be printed at a store's printer. Of course, you would suddenly get piracy and DRM problems just like other industries that cannot cope without exclusivity.
